Process for removing the combined sulfur from vulcanized rubber.



IUNITED $1 DAVID SPENCE, OF NORWALK, CONNECTICUT. I

PROCE$S FOR REMOVING THE COMBINED SULFUR. FROM VULCAENIZED RUBBER.

N0 Drawing. Original application filed June 27, 1914, Serial No.847,706.

Deeember'20, 1916.

T0 at! "whom it may concern lie. it known that T. Davin SPI'INHC. asubject of the King of (treat Britain and Ireland, residing at Norwalk.in the county of l airfield and State of Connecticut. have inventedcertain new and useful ,Jmprovements in Processes for Removing the- (onebined Sulfur from Vulcanized Rubber. of which the following is aspecification.

This invention relates to a process for removing the combined sulfurfrom vulcanized rubber. and its novelty consists in the severalsuccessive steps employed to secure the desired result.

This application. by a re p irement of the Patent Office. is a divisionof my application for Letters Patent of the United States. Serial No.M7506. filed June 97th, 1914-.

In the principal application of which this is a division. I havedescribed a method of treating vulcanized rubber which consists brieflyfirst in removing therefrom in any usual manner the uncombined sulfur.second dissolving the vulcanized rubber so freed from impurities in asuitable solvent, and third while in such solution. subjecting it at asuitable temperature to the action of a reagent capable of uniting withthe sulfur when freed from the rubber. the reaction taking place in the.presence of a vul .anizing accelerator. It was also stated in thatapplication that the reagent acting as the vulcanizing accelerator andthe reagent vapable of uniting with the free sulfur might be identical.that is. one reagent might perform the double function. And it wasfurther stated that the reaction should take place under anhydrousconditions. The principle underlying the process of the describedapplicationis thatlreagents capable of accelerating the unioi of sulfurwith rubber to form vulcanized rubber. are generally speaking capable ofaccelerating the .reverse reaction when it is desired to destroy thecom-- bination between the sulfur and the rubber. Among the reagentssuitable for use in rarrying out the process is caustic soda. Forinstance. the followin process has been performed: Ten parts ofvulcanized rubber waste from which the free sulfur had been extracted,was heated with twenty-five parts of powdered anhydrous caustic soda andtwo hundred partsof Xylol for three hours at 140 centigrade in anautoclave provided Specification of Letters Patent.

Patented Ad "z, 1917.

Divided and this application filed Serial No. 137,954.

with means for agitation. the rubber waste is thus first dissolved orpartially dissolved in the xylol and the powdered alkali is added whilevigorous agitation is maintained throughout the mass. The solution wasthen centrifuged till free from insoluble sultids and other insolublematter and was then treated with a small quantity of lrvdrochloric acidto decompose the last traces ofalkali and alkaline sulfids present. andthe rubber was precipitated from the solution by acetone. It might beisolated by any other well known means. By repeated boiling out withwater. followed by thorough washing with cold water on the mill, a toughI elastic sheet of rubber-like substance was obtained. In the case ofthe sample of vulcanized rubber which contained 4.1% of combined sulfurtreated in this way, the combined sulfunwas reduced to 1.2%, that I is70% of the combined sulfur was removed in one operation. It is obviousthat by a further similar tr atment afurther portion of such combinedsulfur might be removed.

1 claim:

l. The method of removing combined sel fur from vulcanized rubber whichconsists in treating the dissolved rubber with anliydrous or nearlyanlrvdrous caustic alkali.

The method of removing combined sulfur from vulcanized rubber whichcoi-isists in dissolving the rubber in a solvent; and traiting it withan excess of finely divided approximately anhydrous caustic allt-ali. I

3. The method of removing combined sulfur from vulcanized rubber whichconsists in treating it. in solution in xylol. with an excess of finelydivided caustic soda, ,intl'ie substantial absence of moisture. i 4.,The process of removing combinedg'suh fur from vulcau md rubber, whichfconsists first in removing therefrom in any usu'al manner theuncombined sulfur, second dissolving the vulcanized rubber so freed fromim iiurities in a suitable solvent, third adding thereto at a suitabletemperature anhydrous caustic alkali under conditions of agitation, andfourth -'precipitating the rubber from the solution.

5. The process of removing combined sulfur from vulcanized rubber, whichconsists in subjecting the vulcanized rubber in solu- 5' tion to theaction of anhydrous caustic alkali 3 in a finely divided state at asuitabld-Item-E perature and under conditions of agitation adding asuitable quantity. of an aciil Le neutralize the alkaline ingredientsremaining in the solution. and precipitating the 5 rubber from thesolution.

6. The process of treating vulcanized llll) her. which consists first inreumving there from the llllCOllllJllltll sull'lut, SCtUlltl dissolving:the ltslllllfl in a suitable solvent aml sillijet-ting the dissolvedrubber to tl e action of an anli;\' lr0us or nearly anltvdmuls causticalkali. v r

In witness \vliereaf-l allix m signature.

DA VID swivels.

